Fluid conducting rotary joints or swivel joints are known in the art for transmitting high pressure operating fluid, such as hydraulic fluid, in heavy equipment with moving parts such as lifting devices, log loaders, cranes and material handling equipment. These are also known as fluid conducting swivel joints which are especially useful for equipment that lifts and rotates. Examples of specifications of conventional fluid conducting swivel joints are represented by copy of a catalog from Hydraulics, Inc. of Fort Worth, Tex., in which the cover page and pages 7, 9 and 27 are attached as an Appendix and incorporated by reference.
The conventional fluid conducting rotary joint transmits fluid under pressure from a pump source to hydraulic cylinders or other fluid operated equipment. The joint may also return fluid under reduced pressure from the fluid system back to pump supply. They generally include a stem portion with an integral hex drive nut and threaded portion which screws into the threaded connection of a source of pressurized fluid by means of a wrench which tums the drive nut on the connection end of the joint. A closely fitted barrel is supported on the remainder of the stem. Fluid volume rated flow path through these mating components is arranged to divert flow direction 90 degrees. The barrel has an outlet port in communication with an opening in the connection end of the stem through a fluid chamber or annulus in the center of the swiveling portion of the joint. Longitudinally spaced inner and outer bearing surfaces on the outside of the stem and the inside of the barrel are interengaged. Spaced-apart seals separate the bearing surfaces and form a transfer chamber where rated volume flow of fluid may be bi-directionally transferred from the interior of the stem to a confined area between the stem and barrel which leads to an opening in the barrel with a connection to an output line.
The geometry of joint installations, heavy and abusive loads, wear and dangerous operating pressures impose severe constraints on rotary joint construction. Many of these joints are required to operate at 3,000 psi. Advances to fluid power operating pressures in machinery demand operation of even higher pressures with good fluid throughput. Designers design on the basis of obtaining about 15 feet/second velocity through conductors of a nominal given bore size. This establishes the rated flow volume for each component. Current rotary joint support bearings are taxed by these requirements and are often short lived causing down time and high maintenance expense in the field. Current rotary joint seal gland clearances and especially the increase in these clearances from support bearing wear result in reduced seal life. Increased fluid pressure causes premature failures. Even a small gap between the bearings of the stem and barrel permits extrusion of the "O"-ring seals causing damage which results in leakage and ultimate failure of the seals.
Furthermore, mobile equipment engineers and others are driven to reduce equipment size for cost and weight reduction and this has resulted in a need for a reduced component size to fit in smaller spaces. Finally, loss of hydraulic fluids from such joints is becoming less tolerated due to a desire to protect the environment. Fluid loss from short lived products with unpredictable performance is not acceptable and price premiums are becoming common for products which can overcome these shortcomings. The stem installation clearance is the height of the joint above the primary fluid connection. It would be desirable to produce a high pressure rotary joint of rated volume having a reduced stem installation clearance to fit in smaller spaces. It would also be desirable to produce a joint for the same stem installation clearance with an increased barrel height and longer bearing surfaces to produce a rotary joint with greater wear resistance, strength and the ability to operate under higher pressures without extruding the seals. It would be desirable to produce a rotary joint of rated volume fluid flow for the same stem installation clearance wherein the stem and barrel side load angle of misalignment caused by loads placed on the barrel by hanging hoses is significantly reduced as compared to conventional rotary joints with equal diametrical clearance between the stem and barrel. Reduction of side load angle misalignment reduces the tendency of the seals to extrude under pressure and allows higher operating pressure under severe conditions. It would be desirable to produce these results without compromising support bearing length, fluid throughput velocity and volume and without requiring special installation and removal wrenches which are not commonly available in the field. The invention herein disclosed accomplishes all these purposes and more.